docs: def unique_scene_labels(scene_list):
      """Find the unique scene labels
  
      Parameters
      ----------
      scene_list : list, shape=(n,)
          A list containing scene dicts
  
      Returns
      -------
      labels: list, shape=(n,)
          Unique labels in alphabetical order
  
      """
      if isinstance(scene_list, dcase_util.containers.MetaDataContainer):
          return scene_list.unique_scene_labels
  
      else:
          labels = []
          for item in scene_list:
              if 'scene_label' in item and item['scene_label'] not in labels:
                  labels.append(item['scene_label'])
  
          labels.sort()
          return labels